Power settings

What power setting do you use?

  • Rental power (full power)

    Votes: 6 9.4%

  • 75% all the time

    Votes: 18 28.1%

  • 65% good trade off for speed/efficiency

    Votes: 24 37.5%

  • 55% I'm in no hurry

    Votes: 2 3.1%

  • < 55% no place to go

    Votes: 0 0.0%

  • Depends on the mission.

    Votes: 14 21.9%
  • Total voters
    64
Iceman

Iceman

Pre-takeoff checklist
Joined
Apr 27, 2005
Messages
374
Location
Kalamazoo, MI
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Display name:
Chris
I was just wondering what everyone thought was a good place to run an engine after it is broken in. Do you like to go as fast as possible? Do you like to save fuel? Does it depend on your mission?
 
Iceman said:
I was just wondering what everyone thought was a good place to run an engine after it is broken in. Do you like to go as fast as possible? Do you like to save fuel? Does it depend on your mission?
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65% +/- 5% is generally considered a good compromise between speed and fuel economy. Typically, if you push to 75% or more you are getting a few more knots for a lot more gas. And anything beyond 75% requires a very rich mixture on most because the cooling system isn't designed to shed that much heat.
 
I usually use 65%. 75% doesn't seem to provide a worthwhile difference in speed compared to the extra noise and vibration.

I don't like "rental power," despite being a renter myself. Thrashing the engine costs the owner more, and therefore costs me more.
 
Joe Williams said:
I don't like "rental power," despite being a renter myself. Thrashing the engine costs the owner more, and therefore costs me more.
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Thats a good point. If I owned an aircraft on the flightline your the type of renter I would like :yes:.
 
Depends on the mission, but usually as fast as is safely possible.

Iceman said:
I was just wondering what everyone thought was a good place to run an engine after it is broken in. Do you like to go as fast as possible? Do you like to save fuel? Does it depend on your mission?
Click to expand...
 
'47H is very economical in most power ranges. I measured it during one 7 HOUR mission which included several cycles and found it used about 6.5 gallons an hour. Someone blamed it on excessive leaning but truth told, lean or not, the average is 6.5-7 gallons.
65% is a good cruise setting which gives you a good indicated, most times a good ground speed, and good economy. Full rental power doesn't really do much for you.
 
Iceman said:
I was just wondering what everyone thought was a good place to run an engine after it is broken in. Do you like to go as fast as possible? Do you like to save fuel? Does it depend on your mission?
Click to expand...

In a hurry? 75%
Not? 65%

Our club seems to curb "rental power" by charging tach time for the rentals. Push the engine hard and you're going to pay a good bit more.
 
Running the A-36 LOP, I can normally burn over 16 gph. Where I run the engine generally produces 14.9hp per gallon burned at 50 degrees LOP. That produces 238 HP on an engine rated for 300 or 79% power. Sometimes I can increase the burn rate slightly if OATs aren't high. In the winter, low, I can produce more, but normally don't go over 16.5 gph. Often, I run further LOP which produces a little less power to keep cylinder head temps below 180.

Dave
 
180 for cylinder head temps is pretty cold. Are those Fahrenheit degrees, Dave?
 
Bill Jennings said:
In a hurry? 75%
Not? 65%

Our club seems to curb "rental power" by charging tach time for the rentals. Push the engine hard and you're going to pay a good bit more.
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Is the tach showing that much of a difference between 75% and 65%? It seems to me that the total difference between the hobbs and tach is relatively small.
 
AirBaker said:
Is the tach showing that much of a difference between 75% and 65%? It seems to me that the total difference between the hobbs and tach is relatively small.
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Well, it deppends on how you look at it. 75% to 65% is 10% difference. That boils down to 6 minutes per hour (.1) and at $95/hour that's $9.50. If you fly 100 hours per year that's $95 savings or one extra hour of flying for free :D.
 
Wouldn't it be ~10 times more $ ?

Useful yes, but I'm not out there flying to save money, just myself.

waldo said:
Well, it deppends on how you look at it. 75% to 65% is 10% difference. That boils down to 6 minutes per hour (.1) and at $95/hour that's $9.50. If you fly 100 hours per year that's $95 savings or one extra hour of flying for free :D.
Click to expand...
 
AirBaker said:
Is the tach showing that much of a difference between 75% and 65%? It seems to me that the total difference between the hobbs and tach is relatively small.
Click to expand...

Actually, its based on revs. On our planes, about 2400rpm gives you about 1:1 tach to hobbs. Push it to 2600rpm, and you're paying about 120% of Hobbs. So that $89/hr price just went to $107/hr. Trivial for some, but maybe not others.
 
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